The Space Pen (also known as the Zero Gravity Pen)is a penthat uses pressurised inkcartridges and is claimed to write in zero gravity, upside down, underwater, over wet and greasy paper, at any angle, and in extreme temperatureranges. The pen can write at altitudes up to 12,500 feet (3810 m). The ballpoint is made from tungsten carbideand is precisely fitted in order to avoid leaks. A sliding float separates the ink from the pressurized gas. The thixotropicink in the hermetically sealedand pressurised reservoir is claimed to write for three times longer than a standard ballpoint pen. The ink is forced out by compressed air at a pressure of nearly 35 pounds per square inch. Operating temperatures range from -35 to 120 degrees Celsius. The pen has an estimated shelf life of 100 years.
